Volume control



March 17, 1931. KENT 1,796,375

VOLUME CONTROL Filed 1928 2 Sheets-Sheet 1 F miaozw March 17, 1931. T 1,796,375

VOLUME CONTROL Filed Jan. 11, 1928 2 Sheets-Sheet 2 Z'Z i FIG 2i 747 ///5 ATTOR/KEX Patenttl Mar. 17, 193i PATENT OFFICE ARTHUR ATWATER KENT, 0F ARDMORE, PENNSYLVANIA VQLUME CONTIRQL Application filed January 11, 1928. Serial No. 245,851.

My invention relates to the control of volume or magnitude of amplification in radio receiving systems, and more particularly those in which the source of power for the anode circuits and cathode heating is of the alternating current type.

In accordance with my invention a resist ance, which may be non-inductive or more or less inductive, is suitably related to a coupling transformer to effect volume control and is characterized by the fact that for equal increments of movement of the control contact different magnitudes of resistance change are etiected. While this may be effected by various arrangements, a simple one comprises a resistance of a plurality of sections of such character or so disposed that the increments of resistance change for equal increments of movement of the control contact is different in the difierent sections; or the resistance conductor may be wound in equally spaced turns upon a tapered form or in unequally spaced turns upon an untapered term.

Further in accordance with my invention a volume-controlling resistance of the character aforesaid is associated with each of a plurality of coupling transformers in diderent stages, with their control contacts movable in unison and so cooperatively related to their resistances that the latter are in effect staggered, whereby the control contacts in their movement do not simultaneously close circuit through their associated resistances.

My invention resides in a system of volume control of the character hereinafter described and claimed.

For an understanding of my invention and for an illustration of some of the various forms it may take reference is to be had to the accompanying drawings in which:

Fig. l is a diagrammatic view of a receiving system or set provided with my invention.

Fig. 2 is an illustration of a modification.

Fig. 3 is a top plan view of a multiple volume control unit.

Fig. 4 is a vertical sectional View on the line 22 of Fig. 3, with parts in elevation.

Fig. 5 is a bottom plan view of the struc ture shown in Figs. 3 and 4.

Fig. 6 is a side view of a tapered resistance unit.

Referring to Fig. 1, that part thereof to the left of the line represents a radio receiving system or set, while the portion to the right of that line represents the sources of alternating current for heating cathodes or filaments of the tubes and for supplying rectified filtered alternating current to the anode or plate circuits of the tubes.

G represents generally any suitable source of alternating current from which extend the conductors l and 2 to a lamp socket, plug receptacle or equivalent switching means 3 through which communication is effected with the primary at of a transformer having the secondaries 5, 6 and 7 delivering low voltage alternating current for heating the cathodes or filaments of the vacuum tubes while the secondary 8 delivers current for heating the filament of cathode f of the'rectifier tube 9 whose anodes a, a are connected to the terminals of the secondary 10. The rectifier 9 and its assoclated filter system comprising choke coils, condensers and resistances as indicated constitute a source of current for the anode circuits of the tubes, the several. leads 11, 12 and 13 supplying plate circuit curent at different suitable voltages.

The received electro-radiant energy is absorbed by the antenna A or any other equivalentabsorption structure, as a loop, etc. In the example illustrated between the antenna A and ground, earth or countercapacity E is connected the primary of a step-up transformer T across whose secondary is connected the tuning condenser C one of Whose terminals is connected through the stabilizing resistance R with the grid 9 of the first amplifier tube V having the usual anode a and cathode or filament f. In the anode circuit of the tube V is the primary P1 of a step-up radio frequency transformer T1 whose secondary is tuned by the condenser C1 one of whose terminals is connected through the stabilizing resistance R with the grid of the second amplifier tube V1 in whose anode circuit is the primary P2 of a step-up radio frequency transformer T2 whose secondary is tuned by the condenser C2 one of whose terminals connects through the grid condenser is with the grid of the detector tube V2 and whose other terminal connects with the equipotential cathode f1 maintained at electronemitting temperature by the heater resistance 72,. Between grid 9 and cathode fl is connected the usual high resistance leak 1*. Between the cathode f1 and the anode a is a suitable condenser I01 and in the anode circuit is the primary of an audio frequency transformer T3 whose secondary is connected to the'input electrodes of the audio frequency amplifier tube V3 in whose anode circuit is the primary of the audio frequency transformer T4 whose secondary is connected to the input electrodes of the audio frequency amplifier tube V4 whose anode is connected through the condenser 722 with one terminal of the signal translating instrument, such as the loud speaker L whose other terminal is connected with the middle of the resistance 11 connected across the terminals of the oathode f. In series with the conductor 11 is the choke coil 6 connecting with the anode of the tube V4.

The cathode of the tube V4 is in circuit with the secondary 5; the heater resistance h of the tube V2 is in circuit with the secondary 6; and the cathodes of the tubes V, V1, and V3 are in parallel with each other in the circuit of the secondary 7.

The conductor 11 is connected to earth or countercapac-ity E through the condenser I03, and the terminals of the cathodes of the tubes V and V1 are connected to earth or countercapacity E through the condensers I04 and 705. The radio frequency path from anode to cathodes of the tubes V and V1 1 is through these condensers k3, 7:4

- and k5.

The system and apparatus as thus far described is atypical tuned radio frequency receiver-whose power source is of the alternating current type.

The control contact K1 connected through the conductor 11 with one terminal of the primary P1 is movable along the resistance R1 whose terminal 14 is connected through conductor 14a to the other terminal of the primary P1 whereby a variable portion of the resistance R1, between terminal 14 and contact K1, is in shunt to the primary P1. With the entire resistance R1 out of circuit maximum amplification or volume is obtained and as the resistance R1 is brought into circuit and reduced the magnitude of amplification and volume are reduced, be cause the radio frequency voltage impressed upon the input electrodes of the amplifier V1 is reduced. Such arrangement is per so not my invention and is of broadly and generally the character of the volume control disclosed in Millers application Serial No.

1,7eas75 253,116, filed February 9, 1928, and in Me- Laughlins application Serial No. 255,325, filed February 18, 1928. y

In accordance with my invention however, the resistance R1 is of such character or so constructed that for equal increments of movement of the contact K1 unequal increments of resistance change are effected. This may be acomplished in various ways as by utilizing throughout the resistance R1 a conductor having uniform resistance per unit of length but with the number of turns per unit of angular movement of the contact K1 decreasing toward the terminal 14, as described in my application Ser. No. 249,785, filed January 27, 1928, patented September 9, 1930, No. 1,77 5,399'; or, as'indicated, the resistance R1 may be formed in'two sections 15 and 16 of widely different specific resistances or of widely different resistances per turn. The resistance 16 is relatively small While 15 is relatively large. For example the resistance 16 may be of copper wire while 15 may be of advance or other high resistance wire. Further by Way of example the total non-inductive resistance of 16 may be of the order-of 2 or 3 ohms while the non-inductive resistance of 15 may be of the order of 350 ohms where the primary P is of few turns and is utilized in a receiving system for wave lengths ranging from about 200 to about 600 meters. In sweeping over the resistance 16 the contact K1 varies by small increments a small resistance invshunt to the primary P1 while in sweeping over the resistance 15 varies by greater increments the shunting resistance. As the contact K1 'is moved clockwise the shunting resistance is progressively decreased, decreasing the volume of reproduction in the speaker L.

After crossing the joint 17 between the resistances 15 and 16, and in the region of low volume the increments of movement because of the low resistance of 16 may be quite considerable without need for delicacy by an operator in effecting small resistance changes. A second control contact K2 engages a second similar volume control resistance R2, in shunt to the primary P2 of the transformer T2 of the next stage, thereby effecting simultaneous volume control in a plurality of stages. The resistance R2 comprises high and low resistance sections 18 and 19 generally of the characters and relations of the resistance sections 15 and 16. The contact K2 is connectedthrough conductors 11 with one terminal of the primary P2 and the terminal 20 is connected through conductor 20a to the other terminal of the primary P2.

With the contacts K1 and K2 rotated counterclockwise to position beyond the ends 15a and 18a of the resistances R1 and R2 respectively, those resistances are not in circuit and there is no shunting effect upon either pri mary P1 or P2 with the result that there is essrs obtained maximum amplification or volume. To reduce the volume the contacts are rotat ed in clockwise direction, from the position last assumed, and the contact K1 will first engage the end 18a of the resistance R2, bringing that resistance into circuit to cause a reduction in amplification or volume. Later, upon further clockwise rotation of the contacts, K1 will engage the end a of the resistance R1 causing a shunting efiect upon the primary P1 with further reduction of volume. The resistances R1 and R2 are in effect staggered in that their respective contacts close circuit through them dissimultaneously, thereby causing dissimultaneous clicks incident to circuit closures through the resistances, with less oflense to the listener than in the case the circuit closures. were simultaneous, which would cause considerable noise due to the relatively great and sudden increase in shunting effects upon the two coupling transformers.

While in the arrangement indicated in Fig. 1 contact K2 first closes circuit with resistance R2, it will be understod that the shunting effect may be first applied to the earlier stage primary Pl, by causing the contact Kl to engage the resistance El before contact K2 engages resistance R2.

It is preferred as indicated that the arouate extents of the resistances l6 and 19 be somewhat different whereby the contacts Kl and K2 will not the same time traverse the joints 1'? and 2i, with the result that double volume control will he smoother with less apparent sharp changes in volume as the control contacts move from one resistance section onto another, The resistance sections are therefore also in eilect staggered as be tween the resistances R1 and R2.

A indicated in Fig. 2 the contacts i and K2, which close circuit at i501 and 180; in succession, are directly connected to earth or countercapacity E; and in the connections l lo and 20a from the terminals and 20 their corresponding terminals of the primaries P1 and P2 are disposed series condensers 746 and 767, this modification being of a character disclosed in the aforesaid Mc- Laughlin application.

lln {i there is shown a resistance R1 whose conductor is disposed in uniformly spaced turns upon the tapering plate or "form 32a, whereby for equal increments along the resistance by the contact Kl there will be ettected greater resistance changes in the vicinity of the end, 1512 than in the vicinity of the end or terminal l l. The resistance conductor in Fig. 6 is of the same diameter and material throughout, though it will be understood that it may be a conductor or difierent specific resistances in ditlerent portions and in this latter case the copper section, for in tance, would again be at the end adjacent theterniinal ll. lln multiple control, utilizing two or more resistances of the character shown in Fig. 6, it is desirable again to stagger them so that circuit closures secured the spring contact plate 28 whose opposite ends constitute the aforesaid control contacts Kl and K2. Engaging in a groove in the shaft 24 is a contact spring .29 secured to the casing 25 by the screw which also holds the terminal 31 which latter as indicated in Fig. 1 is connected to the conductor ll, and is also connected through the spring 29 with the contacts Kl,

T he conductors constituting the resistances R1 and R2 are wound transversely around flexible strips or plates 82 of insulating ma terial such as bakelized canvas or the lilre. The arcuate resistance units are held in place adjacent the inner wall of the casing 22 by screws or bolts 33.

ln the example illustrated the turns of resistance conductor, in each section, are substantially uniformly space Further by way of example the low resistance sections 16 and 19 may be No. 3G copper wire, and sections 15 and may he No. 38 advance wire which has a specific resistance oi the order of twenty times that of copper. The end of the resistance conductor 16 is electrically connected to a terminal 14 held by the same bolt 33 which secures the adjacent end of the strip Similarl the end of the conductor l9 is connected to e terminal 20 which is secured by the same bolt-33 which secures the adjacent 32 upon which conductor 19 end of the strip is wound.

To vary the magnitude or amplification or control volume ml reproduction the operator turns the lrnob 25 in appropriate direction, counterclockwise in 3, to reduce volume.

The resistance units comprising conductors wound upon strips as described in connection with Figs. 3-5, are not strictly noninductive resistances, but are to an appreciable or substantial extent inductive, since the conductor is in the form oil what might be termed a helix of rectangular crosssection. In efi'ect therefore a variable impedance or inductive resistance is so opereratively related to a coupling transformer as to control amplification or volume. Be-

cause of the inductance of the winding of each resistance unit the impedance thereof at radio frequency is materially in excess or" the simple non-inductive or ohmic resistance llltl ill) of the wire constituting the unit. Where the conductor is wound upon a flat or' thin strip such as 32 the/ ratio of the resistance to the inductance per turn, because the area enclosed by a turn is small,; is relatively higher than where the area enclosed by the turn is circular in which case :the area enclosed per unit length of resistance wire' is greater.

Furthermore the ratio of resistance to inductance in the low resistance or copper section as 16 or 19 is smaller than in the higher resistance section 15 or 18, and as regards the low resistance sections 16 and 19 the eflective impedance may be materially greater than the non-inductive resistance as when the reactive component of the meaave be greater and of the order of the impedances of the inductive forms described.

The receiving system is tuned by suitable adjustment of the condensers G, C1 and 02.

If desired their rotors may be mechanicallycoupled whereby the three circuits may be any of them, to de-tuned position. And it impedance is of the order of or greater than the non-inductive component. At the high frequency portion of the range for'which the system or set is designed and tunable the treactive component of the impedance throughout each resistance R1 and RQ is greater than at the low frequency portion of the range.

Where the turns of the resistance conductor are uniformly spaced upon an untapered form or core 32, as in Figs. 4: and 5, and where the total non-inductive resistance of each unit is of the order of 350 ohms, the

inductance is about microhenrys, yielding an inductive reactance of the order of 200 ohms at the low frequency of the range and of the order of 600 ohms at the high frequency. of the range. Hence at the high frequency end of the range the impedance is of the order of 700 ohms, of which, as aforesaid the -non-inductive component is 350 ohms and the reactive component about .600 ohms. The impedance is somewhat further increased by the distributed capacity of the resistance winding. In the copper sections as 16 and 19 the inductive reactance may be of the order of from about 35 to about 100 ohms, atthe low and high frequencies respectively, and with a non-inductive resistance of the order of 2 or 3 ohm-s, it is apparent that the reactance predominates over the non-inductive resistance and that the impedance is roughly equal to but slightly greater than the inductive reactance.

In a resistance unit of the character indicated in Fig. 6 the inductance per turn is less in the vicinity of the terminal 14 than at the end 15a. I

In all of the inductive arrangements described'however the efiective shunting impedance is diiferent'for difi'erent increments of movement of the contact along the resistance unit.

It shall be understood howeverthat strictly non-inductive resistances as well as inductive resistances are contemplated by my invention. Where the resistances are non-inductive however their magnitudes will is further the fact that the type of volume control involved is of a character which does not increase the tendency to production of hum when the power source is of the alternating current type. The reverse poling of the windings of the transformers T1 and T2 as indicated, together with the stabilizing resistance R and the inherent capacity between the high potential terminal of the secondary of the transformer T2 and the grid of the tube V1 efiiects stability throughout the till wave length range for which the system is tunable. Uther systems such as balanced or neutralized systems may also be employed, as well understood in the art. The stability or neutralization of such systems is however not materially aifected b the type of volume control herein disclose With high step-up ratios in the transformers, as of the order of ten, the eflects of the resistances R1 and R2 upon the selectivity of the circuits tuned by the condensers C2 are maintained correspondingly low.

It shall be understood that a volume control resistance of the character and efiect described may be associated with any of the other transformers as T, T3 and T45, and a plurality of such control resistances may be associated with any two or more of the transformers T to Tet inclusive-and their control contacts may be actuated in unison. lln general the control resistance may have the described shunting efiect either upon' the primary or secondary of any of the transformers but it is preferred that it be associated with the primary of the transformer, and

particularly with the primary of any of the radio frequency transfromers T, T1 and T2, particularly when the transformer hasa substantial or high step-up ratio.

The term resistance, as employed in the appended claims shall be understood to comprehend both inductive and non-inductive resistances:

What I claim is:

1. Receiving apparatus comprising in combination a path traversed by undulatory current, a transformer having its primary in said path, a thermionic device having its input electrodes operatively related to the secondary of said transformer, and means for controlling the volume of reproduction comprising a resistance and a cooperating control contact for causing a variable shunting efiect upon the primary of said transformer, equal increments of movement of said control contact along said resistance efiecting different impedance changes, the resistance being so connected that smaller impedance changes are effected in the region of low volume than in the region of high volume.

2. lteceiving apparatus comprising in combination a path traversed by radio frequency current, a step-up transformer hav- 1ng its primary in said path, a variable condenser forming With the secondary of said transformer a tunable circuit, a thermionic amplifier having its input electrodes operatively related to said tunable circuit, and means for controlling the magnitude of am plilication comprising a resistance and a coacting control contact having a shunting effect upon the primary of said transformer, equal increments of movement of said control contact along said resistance etlecting difi'erent impedance changes, the resistance being so. connected that smaller impedance changesare effected in the region of loW volume than in the region of high volume.

3. Receiving apparatus comprising in combination a path traversed by undulatory current, a transformer having its primary in said path, a thermionic device having its input electrodes operatively related to the secondary of said transformer, and means for controlling the volume of reproduction comprising a resistance and a cooperatingcontrol contact for causing a variable shunting eilect upon the primary of said transformer,

an increment of movement of said control contact effecting a smaller impedance change in the region of great shunting effect than the impedance change for an equal increment of movement of said contact in a region of lesser shunting efiect.

l. Receiving apparatus comprising in combination a path traversed by undulatory current, a transformer having its primary in said path, a thermionic device having its input electrodes operatively related to the secondary of said transformer, and means for controlling the volume of reproduction comprising a resistance and a cooperating control contact for causing a variable shunting efiect on one of the windings of said transformers, said resistance comprising sections in each of Which the increments of impedance change are equal for equal increments of movement of said control contact, and the increments of impedance change in diil'erent sections losing unequal for equal increments of movement of said. control contact and less in the region of low volume than in the region oit high volume.

5. In a receiving system comprising a path traversed by undulatory current, a thermi= Ohio device, means coupling the input circuit of said device to said path, a second thermionic device, means coupling the output circuit of said first device to the input circuit of said second device, a resistance and a cooperating control contact associated With each of said coupling means, and means mechanically coupling the control contacts to cause their movement in unison, said resistances and said control contacts being so related to each other that said control contacts close circuit through their associated resistances in succession.

6. Receiving apparatus comprising in combination cascaded thermionic devices, a transformer Whose secondary is operatively related to the input electrodes of one of said thermionic devices, a second transformer Whose secondary is operatively related to the input electrodes of another of said thermionic devices and Whose primary is influenced by the current in the output circuit of said one of said thermionic devices, and means for controlling the volume of reproduction comprising for each 01" said transformers a resistance and a coacting control contact having a shunting effect on a Winding of the transformer, and means mechanically coupling said control contacts to cause their movement in unison along their associated resistances to effect change in the same sense of their shunting efiects, each ofsaid resistances having the characteristic that difierent increments oi? impedance change are efi ected hy equal increments of movement of the control contact, the resistance being so connected that in each smaller impedance changes are efiected in the region of low volume than in the region of high volume.

7 Receiving apparatus comprising in combination cascaded thermionic devices, a transformer vvhose secondary is operatively related to the input electrodes of one of said thermionic devices, a second transformer Whose secondary is operatively related to the input electrodes of another of said thermionic devices and Whose primary is influenced by the current in the output circuit of said one of said thermionic devices, and means for controlling the volume of reproduction comprising for each of said transformers a resistance and a coacting control contact having a shunting efiect on Winding of the transformer, and means mechanically coupling said control contacts to cause their movement in unison along their associated resistances cumulatively to afi'ect volume, each of said resistances comprising sections in each of which the increments of impedance change are equal for equal increments of movement of said control contact, and the increments of impedance change in difierent sections being unequal for equal increments of movement of said control contact, the resistances being so connected that in each smaller impedance changes are eifected in the region of low volume than in the region of high volume.

8. Receiving apparatus comprising in combination cascaded thermionic devices, a transformer Whose secondary is operatively related to the input electrodes of one of said thermionic devices, a second transformer whose secondary is operatively-related to the input electrodes of another ofsaid thermionic devices and Whose primary is influenced by the current in the output circuit of said one of said thermionic devices, and means for controlling the volume of reproduction comprising for each of said transformers a resistance and a coacting control contact having a shunting eifect on a winding of the transformer and means mechanically coupling said control contacts to cause their.

movement in unison along their associated resistances, said resistances being staggered with respect to each other, whereby said control contacts close circuit through them in succession.

9. Receiving apparatus comprising in combination cascaded thermionic devices, a transformer Whose secondary is operatively related to the input electrodes of one of said thermionic devices, a second transformer Whose secondary is operatively related to the input electrodes of another of said thermionic devices and Whose primary is influenced by the current in the output circuit of said one of said thermionic devices, and means for controlling the volume of reproduction com' prising for each of said transformers a resistance and a coacting control contact. having a shunting efiect on a Winding of the transformer, and means mechanically coupling said control contacts to cause their movement in unison along their assaciated resistances to effect change in the same sense of their shunting efiects, each of said resistances comprising sections in which different resistance changes are efiected for equal increments of movement of the control contact, the sections of one of said resistances being staggered with respect to the sections of another of said resistances whereby said control contacts may not'simultaneously be moved from one section to another.

10. Radio receiving apparatus comprising an absorption circuit, a plurality of thermionic tubes and associated circuits for amplifying signal energy impressed upon said absorption circuit, means for controlling the volume of reproduction of signals comprising impedances disposed respectively in different circuits, and .a common operating means for said impedances, the construction and relation of said impedances being such that in adjustment of said common operating means therefor to change the volume from one amplitude to another, the cumulative individual efitects of the resistances have a diiferentrate of variation.

mortars 11. Radio receiving apparatus comprising a thermionic tube for amplifying radio-frequency signal energy, means for controlling the volume of reproduction of signals comprising impedances disposed in difierent circuits of said tube, and a common operating means for said impedances, the construction and relation of said impedances being such that in adjustment of said common operating means therefor to change the volume from one amplitude to another, the cumulative individual efiects of the resistances have a different rate of variation.

12. Radio receiving apparatus comprising All ATWATER KENT. 

